FIELD_OP_UNARY_MINUS
if (field->operator == FIELD_OP_UNARY_MINUS) {
field_op = FIELD_OP_UNARY_MINUS;
case FIELD_OP_UNARY_MINUS:
expr->operator = FIELD_OP_UNARY_MINUS;
if (field_op == FIELD_OP_UNARY_MINUS)